It is known to make diphenylmaleic anhydride by condensation of potassium benzoylformate with phenylacetic acid (C. P. Koelsch, et al., J. Org. Chem., 6, 684, (1941)). The synthesis of phenanthrene-9,10-dicarboxylic anhydride from diphenyl maleic anhydride in air is also reported (M. V. Sargent, et al. J. Chem. Soc., 5544, (1964)). However, the techniques demonstrated in these reports have not been extended to the synthesis of multifunctional compounds such as the di-substituted maleic anhydride compounds and bis(di-substituted maleic anhydide) compounds of this invention which are capable of forming amide-imide polymers, as well as other polymers.
It is also known to make dianhydrides from maleic anhydride as is taught in commonly-assigned Ser. No. 294,322, now U.S. Pat. No. 4,360,657, and Ser. No. 386,891, now abandoned, which are hereby incorporated by reference. It is also known to make polyimides from dianhydrides and aromatic amines. This is disclosed in U.S. Pat. No. 3,179,634 (1965). British Patent Specification No. 570,858 discloses various processes for making fiber-forming polymers.
In reviewing these references it is clear that the synthesis of di-substituted maleic anhydride and bis(di-substituted maleic anhydride) compounds which are capable of forming amide-imide polymers, polyimides, and vinyl co-polymers has not been contemplated in the prior art. Also, the prior art has not contemplated the preparation of di-substituted maleic anhydride compounds of the structures ##STR5## wherein R, R.sup.1, R.sup.2, and R.sup.3 are defined as heretofore.
The general object of this invention is to provide novel compounds of maleic anhydride structure and novel derivatives of these compounds which are potentially difunctional in structure and to provide novel amide-imide polymers and polyimides. A more specific object of this invention is to provide amide-imide polymers, vinyl polymers, and polyimides from 2-phenyl-3-(p-carboxyphenyl)-maleic anhydride; 2-(m-carboxyphenyl)-3-phenylmaleic anhydride and 2-(o-carboxyphenyl)-3-phenylmaleic anhydride; 3-carboxyphenanthrene-9,10-dicarboxylic anhydride; 2,2'-(1,4-phenylene)bis(3-methylmaleic)anhydride; 2,2'-(1,4-phenylene)bis(3-phenylmaleic)anhydride; 2,2'-(1,4-phenylene)bis(3-(2-phenylethenyl)maleic)anhydride; 2-vinylphenyl-3-phenylmaleic anhydride; 2,2'-(1,3-phenylene)bis(3-phenylmaleic)anhydride; substituted 2,3-diphenylmaleic anhydrides. Another object of this invention is to provide simple procedures for the preparation of these novel maleic anhydride compounds and the polymers which can be prepared therefrom.